1. Field of the Invention
The present invention relates to a positional-deviation correction apparatus, a method of controlling a positional deviation, and an image forming apparatus to obtain an image visualized by superimposing a plurality of colors by an electrophotographic printer and the like.
2. Description of the Related Art
In image forming apparatuses, it is common to perform correction of positional deviation by checking how a test pattern is printed on a recording medium. In the technology disclosed in Japanese Patent No. 3506891, a test pattern is printed on the left and right sides of a recording medium in a conveying direction and includes a first pattern and a second pattern opposing to each other. The first pattern includes stripes formed at a specific interval, and each strip has a specific line width. The second pattern also includes strips formed at a specific interval, and each strip has a specific line width; however, the specific interval is different from the interval of the first pattern.
In color image forming apparatuses, it is common to perform positional alignment of each of the colors. Japanese Patent Application Laid-Open No. 2002-244387 discloses a technology that has a mode for executing each of a plurality of processes, enables a user to select a desired mode and performs positional alignment of the colors appropriate to the user selected mode.
In the related art, a positional-deviation correction apparatus creates images of a plurality of sets of positional deviation correction patterns and detects positional information of each set, in an unambiguous time from start of exposure. However, due to a tolerance in layout size of the positional-deviation correction apparatus, such as a stretching of an intermediate transfer belt, there is an occasion that this unambiguous time cannot be inserted between the respective sets of the correction patterns. This leads to a problem that not all the positional information of the sets of the correction patterns can be read.